Glass material manufacturing method and glass material manufacturing device

ABSTRACT

Provided is a method that can manufacture a glass material having excellent homogeneity by containerless levitation. With a block ( 12 ) of glass raw material held levitated above a forming surface ( 10   a ) of a forming die ( 10 ) by jetting gas through a gas jet hole ( 10   b ) opening on the forming surface ( 10   a ), the block ( 12 ) of glass raw material is heated and melted by irradiation with laser beam, thus obtaining a molten glass, and the molten glass is then cooled to obtain a glass material. Control gas is jetted to the block ( 12 ) of glass raw material along a direction different from a direction of jetting of the levitation gas for use in levitating the block ( 12 ) of glass raw material or the molten glass.

TECHNICAL FIELD

This invention relates to glass material manufacturing methods and glassmaterial manufacturing devices.

BACKGROUND ART

In recent years, studies on containerless levitation techniques asmethods for manufacturing a glass material are being conducted. Forexample, Patent Literature 1 describes a method in which abarium-titanium-based ferroelectric sample levitated in an aerodynamiclevitation furnace is heated and melted by irradiation with laser beamand then cooled to vitrify. Whereas, in conventional methods of meltingglass using a container, contact of molten glass with the wall surfaceof the container may cause crystals to precipitate, containerlesslevitation techniques can reduce the progression of crystallization dueto contact of the molten glass with the wall surface of the container.Therefore, even materials that could not be vitrified by conventionalmanufacturing methods using a container can be vitrified bycontainerless levitation techniques. Hence, containerless levitationtechniques are noteworthy as methods that can manufacture glassmaterials having novel compositions.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2006-248801

SUMMARY OF INVENTION Technical Problem

A challenge for containerless levitation techniques is to improve thehomogeneity of a glass material. To cope with this, in the methoddescribed in Patent Literature 1, a large area of a block of glass rawmaterial is irradiated with laser light using a plurality of lasers.

However, depending on the state of laser irradiation, temperatureunevenness may occur in the block of glass raw material, which may causevolatilization of glass components or generation of unmelted matter.Furthermore, a molten glass in a levitated state obtained by melting theblock of glass raw material may undesirably vibrate or oscillate to comeinto contact with a forming die, thus precipitating crystals. Since, asjust described, the method described in Patent Literature 1 may causeprecipitation of unmelted matter or crystals or undesirablevolatilization, it has difficulty providing sufficiently homogeneousglass.

Moreover, when a glass material is produced by containerless levitation,there is a problem that variations in properties among lots aresignificant.

A principal object of the present invention is to provide a method thatcan manufacture a glass material having excellent homogeneity bycontainerless levitation. Furthermore, a principal object of the presentinvention is to provide a method that can manufacture a glass materialhaving small variations in properties among lots by containerlesslevitation.

Solution to Problem

In a first glass material manufacturing method according to the presentinvention, with a block of glass raw material held levitated above aforming surface of a forming die by jetting gas through a gas jet holeopening on the forming surface, the block of glass raw material isheated and melted by irradiation with laser beam, thus obtaining amolten glass, and the molten glass is then cooled to obtain a glassmaterial. Control gas is jetted to the block of glass raw material alonga direction different from a direction of jetting of the levitation gasfor use in levitating the block of glass raw material or the moltenglass. By doing so, at least one of position and attitude of the blockof glass raw material or the molten glass can be controlled. Thus, theblock of glass raw material can be uniformly irradiated with laserlight. Furthermore, the molten glass can be restrained from coming intocontact with the forming surface. As a result, a glass material havingexcellent homogeneity can be produced.

In the first glass material manufacturing method according to thepresent invention, from the viewpoint of uniformly irradiating thesurface of the block of glass raw material with laser light, the controlgas is preferably jetted during the process of melting the block ofglass raw material.

In the first glass material manufacturing method according to thepresent invention, from the viewpoint of restraining the precipitationof crystals due to contact of the molten glass with the forming die, thecontrol gas is preferably jetted during the process of cooling themolten glass.

In the first glass material manufacturing method according to thepresent invention, the block of glass raw material may be rotated,vibrated or oscillated by jetting the control gas to the block of glassraw material. In this case, the surface of the block of glass rawmaterial can be uniformly irradiated with laser light.

In the first glass material manufacturing method according to thepresent invention, positional change of the molten glass may berestricted by jetting the control gas to the molten glass. In this case,the molten glass can be effectively restrained from coming into contactwith the forming die.

In the first glass material manufacturing method according to thepresent invention, the control gas may be jetted to the block of glassraw material or the molten glass along a horizontal direction or from anupper diagonal position.

A second glass material manufacturing method according to the presentinvention includes the step of heating and melting a block of glass rawmaterial by irradiation with laser light with the block of glass rawmaterial held levitated above a forming surface of a forming die byjetting gas through a gas jet hole opening on the forming surface, thusobtaining a molten glass, and then cooling the molten glass to obtain aglass material, wherein a flow rate of the gas through the gas jet holeafter the melting of the block of glass raw material is smaller than aflow rate of the gas through the gas jet hole before the melting of theblock of glass raw material. By doing so, the block of glass rawmaterial and the molten glass obtained by melting the block of glass rawmaterial can be stably levitated, so that the contact of the block ofglass raw material and the molten glass with the forming die can berestrained. Therefore, a glass material having excellent homogeneity canbe produced.

In the second glass material manufacturing method according to thepresent invention, the flow rate of the gas through the gas jet hole ispreferably reduced before the block of glass raw material is completelymelted. In this case, the molten glass can be restrained from cominginto contact with the forming die and thus forming crystal nuclei or thelike therein.

In the second glass material manufacturing method according to thepresent invention, the flow rate of the gas through the gas jet hole ispreferably increased after the irradiation of laser light is stopped. Bydoing so, the glass material can be kept stably levitated during thecooling step.

A third glass material manufacturing method according to the presentinvention includes: a melting step of placing a block of glass rawmaterial on a forming surface of a forming die, melting the block ofglass raw material by irradiating the block of glass raw material withlaser light while jetting gas through a gas jet hole opening on theforming surface, thus obtaining a molten glass, and then homogenizingthe molten glass; and a cooling step of cooling the molten glass,wherein the irradiation with the laser light is started with the blockof glass raw material in contact with the forming surface and the blockof glass raw material is then levitated above the forming surface by thegas. If the block of glass raw material is irradiated with laser lightwith the block of glass raw material levitated, the position of theblock of glass raw material varies, so that the state of laserirradiation may become unsteady among lots. As a result, variations inproperties of the glass material among lots are likely to occur. Thiscan be attributed to the fact that the local volatilization of glasscomponents caused by irradiation with laser light and the thermalhistory of the block of glass raw material are different among lots.Unlike this, in the glass material manufacturing method according to thepresent invention, the block of glass raw material comes into contactwith the forming surface at least just after the start of irradiationwith laser light, which makes it less likely that the position of theblock of glass raw material varies. Thus, variations among lots in thestate of irradiation of the block of glass raw material with laser lightcan be reduced. Therefore, a glass material small in variations inproperties among lots can be manufactured.

In the third glass material manufacturing method according to thepresent invention, the gas is preferably jetted so that the block ofglass raw material starts being levitated when or before the melting ofthe block of glass raw material is completed. In this case, the moltenglass obtained by melting the block of glass raw material can berestrained from coming into contact with the forming surface. Thus, theprecipitation of crystals in the glass material can be reduced.

In the third glass material manufacturing method according to thepresent invention, a flow rate of the gas is preferably graduallyincreased until the block of glass raw material starts being levitated.In this case, the abrupt change in the flow rate of the gas jetting tothe block of glass raw material can be reduced. Therefore, variations inthe position of the block of glass raw material can be more effectivelyreduced.

In the third glass material manufacturing method according to thepresent invention, a flow rate of the gas is preferably stepwiseincreased until the block of glass raw material starts being levitated.Also in this case, the abrupt change in the flow rate of the gas jettingto the block of glass raw material can be reduced. Therefore, variationsin the position of the block of glass raw material can be moreeffectively reduced.

In the third glass material manufacturing method according to thepresent invention, the gas preferably starts being jetted concurrentlywith the start of irradiation with the laser light. In this case, therise in the temperature of the forming die can be reduced by the coolingeffect of the gas. As a result, the molten glass can be restrained fromadhering to the forming surface of the forming die.

In the third glass material manufacturing method according to thepresent invention, the gas may start being jetted after the start ofirradiation with the laser light. In this case, variations in theposition of the block of glass raw material can be more effectivelyreduced.

A glass material manufacturing device according to the present inventionis a device for manufacturing a glass material by heating and melting ablock of glass raw material by irradiation with laser beam with theblock of glass raw material held levitated above a forming surface of aforming die by jetting gas through a gas jet hole opening on the formingsurface, thus obtaining a molten glass, and then cooling the moltenglass. The glass material manufacturing device according to the presentinvention includes a control gas jetting portion operable to jet controlgas to the block of glass raw material along a direction different froma direction of jetting of the gas for use in levitating the block ofglass raw material. In the glass material manufacturing device accordingto the present invention, at least one of position and attitude of theblock of glass raw material or the molten glass can be controlled.Therefore, the block of glass raw material can be uniformly irradiatedwith laser light. Furthermore, the molten glass can be restrained fromcoming into contact with the forming surface. Hence, a glass materialhaving excellent homogeneity can be produced.

Advantageous Effects of Invention

The present invention can provide a method that can manufacture a glassmaterial having excellent homogeneity by containerless levitation.Furthermore, the present invention can provide a method that canmanufacture a glass material small in variations in properties amonglots by containerless levitation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a glass materialmanufacturing device according to a first embodiment of a first glassmaterial manufacturing method.

FIG. 2 is a diagrammatic plan view of a portion of a forming surface inthe first embodiment of the first glass material manufacturing method.

FIG. 3 is a schematic plan view showing a portion of the glass materialmanufacturing device according to the first embodiment of the firstglass material manufacturing method.

FIG. 4 is a schematic plan view showing a portion of a glass materialmanufacturing device according to a second embodiment of the first glassmaterial manufacturing method.

FIG. 5 is a schematic plan view showing a portion of a glass materialmanufacturing device according to a modification of the first glassmaterial manufacturing method.

FIG. 6 is a schematic cross-sectional view of a glass materialmanufacturing device according to a third embodiment of the first glassmaterial manufacturing method.

FIG. 7 is a schematic cross-sectional view of a glass materialmanufacturing device according to a fourth embodiment of the first glassmaterial manufacturing method.

FIG. 8 is a schematic plan view showing a portion of the glass materialmanufacturing device according to the fourth embodiment of the firstglass material manufacturing method.

FIG. 9 is a schematic cross-sectional view of a glass materialmanufacturing device according to a fifth embodiment of the first glassmaterial manufacturing method.

FIG. 10 is a schematic cross-sectional view of a glass materialmanufacturing device according to a first embodiment of a second glassmaterial manufacturing method.

FIG. 11 is a time chart of the flow rate of gas in the first embodimentof the second glass material manufacturing method.

FIG. 12 is a schematic cross-sectional view of a glass materialmanufacturing device according to a second embodiment of the secondglass material manufacturing method.

FIG. 13 is a time chart of the flow rate of gas in a third embodiment ofthe second glass material manufacturing method.

FIG. 14 is a time chart of the flow rate of gas and the intensity oflaser light in a first embodiment of a third glass materialmanufacturing method.

FIG. 15 is a time chart of the flow rate of gas and the intensity oflaser light in a second embodiment of the third glass materialmanufacturing method.

FIG. 16 is a time chart of the flow rate of gas and the intensity oflaser light in a third embodiment of the third glass materialmanufacturing method.

FIG. 17 is a time chart of the flow rate of gas and the intensity oflaser light in a fourth embodiment of the third glass materialmanufacturing method.

FIG. 18 is a time chart of the flow rate of gas and the intensity oflaser light in a fifth embodiment of the third glass materialmanufacturing method.

FIG. 19 is a time chart of the flow rate of gas and the intensity oflaser light in a sixth embodiment of the third glass materialmanufacturing method.

FIG. 20 is a time chart of the flow rate of gas and the intensity oflaser light in a seventh embodiment of the third glass materialmanufacturing method.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a description will be given of preferred embodiments forworking of the present invention. However, the following embodiments aremerely illustrative. The present invention is not at all limited to thefollowing embodiments.

Throughout the drawings to which the embodiments and the like refer,elements having substantially the same functions will be referred to bythe same reference signs. The drawings to which the embodiments and thelike refer are schematically illustrated. The dimensional ratios and thelike of objects illustrated in the drawings may be different from thoseof the actual objects. Different drawings may have different dimensionalratios and the like of the objects. Dimensional ratios and the like ofspecific objects should be determined in consideration of the followingdescriptions.

In the following embodiments, not only normal glass materials but alsoglass materials having compositions that could not be vitrified bymelting methods using containers, such as for example those free from anetwork forming oxide, can be suitably manufactured. Specifically, forexample, barium titanate-based glass materials, lanthanum-niobiumcomposite oxide-based glass materials, lanthanum-niobium-aluminumcomposite oxide-based glass materials, lanthanum-niobium-tantalumcomposite oxide-based glass materials, lanthanum-tungsten compositeoxide-based glass materials, and so on can be suitably manufactured.

(1) First Glass Material Manufacturing Method

First Embodiment

FIG. 1 is a schematic cross-sectional view of a glass materialmanufacturing device 1 according to a first embodiment. As shown in FIG.1, the glass material manufacturing device 1 includes a forming die 10.The forming die 10 has a curved forming surface 10 a. Specifically, theforming surface 10 a is spherical.

The forming die 10 has levitation gas jet holes 10 b opening on theforming surface 10 a. As shown in FIG. 2, in the first embodiment, aplurality of levitation gas jet holes 10 b are provided. Specifically,the plurality of levitation gas jet holes 10 b are arranged radiallyfrom the center of the forming surface 10 a.

The forming die 10 may be made of a porous body having interconnectedcells. In this case, the levitation gas jet hole 10 b is formed ofinterconnected cells.

The levitation gas jet holes 10 b are connected to a gas supplymechanism 11, such as a compressed gas cylinder. Gas is supplied fromthis gas supply mechanism 11 via the levitation gas jet holes 10 b tothe forming surface 10 a.

No particular limitation is placed on the type of the gas. The gas maybe, for example, air or oxygen or may be inert gas, such as nitrogen,argon or helium gas.

In manufacturing a glass material using the manufacturing device 1,first, a block 12 of glass raw material is placed on the forming surface10 a. The block 12 of glass raw material may be, for example, oneobtained by forming raw material powders for a glass material into asingle piece by press molding or so on. The block 12 of glass rawmaterial may be a sintered body obtained by forming raw material powdersfor a glass material into a single piece by press molding or so on andthen sintering the single piece. Alternatively, the block 12 of glassraw material may be an aggregate of crystals having the same compositionas a desired glass composition.

No particular limitation is placed on the shape of the block 12 of glassraw material. The block 12 of glass raw material may have, for example,a lens-like, spherical, cylindrical, polygonal, cuboidal, oroval-spherical shape.

Next, gas is jetted out through the levitation gas jet holes 10 b, thuslevitating the block 12 of glass raw material above the forming surface10 a. In other words, the block 12 of glass raw material is held, out ofcontact with the forming surface 10 a, in the air. In this state, theblock 12 of glass raw material is irradiated with laser light from alaser applicator 13. Thus, the block 12 of glass raw material is heatedand melted, thus obtaining a molten glass. Thereafter, the molten glassis cooled, so that a glass material can be obtained. The jetting of thelevitation gas is preferably continued until the temperature of theglass material reaches at least below the softening point, preferablybelow the glass transition point, thus restraining the block 12 of glassraw material, the molten glass or the glass material from coming intocontact with the forming surface 10 a.

As shown in FIGS. 1 and 3, the forming die 10 includes a control gas jethole 10 c forming the control gas jetting portion. The control gas jethole 10 c extends in a direction different from the direction ofextension of the levitation gas jet holes 10 b. Specifically, whereasthe levitation gas jet holes 10 b extend along the vertical direction,the control gas jet hole 10 c extends along the horizontal direction.The control gas jet hole 10 c is provided to open to the block 12 ofglass raw material levitated above the forming surface 10 a.

In the first embodiment, with the block 12 of glass raw material heldlevitated, control gas is jetted through the control gas jet hole 10 c.As described above, the direction of extension of the control gas jethole 10 c and the direction of extension of the levitation gas jet holes10 b are different from each other. Therefore, the direction of jettingof the control gas jetting through the control gas jet hole 10 c isdifferent from the direction of jetting of the levitation gas throughthe levitation gas jet holes 10 b. By the control gas jetting throughthe control gas jet hole 10 c, at least one of position and attitude ofthe block 12 of glass raw material or molten glass being levitated iscontrolled.

By employing the above structure, it becomes possible to optimize thestate of irradiation of laser light, so that the precipitation ofunmelted matter or crystals and the occurrence of undesirablevolatilization can be restrained. Therefore, a homogeneous glassmaterial can be produced. More specifically, depending on the state ofirradiation of the block of glass raw material with laser light,temperature unevenness may occur in the block of glass raw material. Ifpart of the block of glass raw material is excessively heated,undesirable volatilization may occur, which may cause problems ofstriae, composition deviation, and so on. On the other hand, if thetemperature of part of the block of glass raw material is too low,unmelted matter may be formed in a produced glass material. Furthermore,if the molten glass in a levitated state undesirably vibrates oroscillates to come into contact with the forming die, crystals may beprecipitated in a produced glass material. To cope with these problems,as described above, in the first embodiment, control gas is jetted tothe block 12 of glass raw material or the molten glass. Thus, at leastone of position and attitude of the block 12 of glass raw material ormolten glass in a levitated state can be controlled.

Specifically, by jetting the control gas during the process of meltingthe block 12 of glass raw material, the block 12 of glass raw materialcan be rotated or can be vibrated or oscillated without coming intocontact with the forming die 10. Thus, the surface of the block 12 ofglass raw material can be uniformly irradiated with laser light. Thismakes it easier to uniformly heat the block 12 of glass raw material. Asa result, the occurrence of undesirable volatilization due to part ofthe block 12 of glass raw material reaching an excessively hightemperature and the generation of unmelted matter due to part of theblock 12 of glass raw material reaching an excessively low temperaturecan be restrained.

Furthermore, by jetting the control gas during the process of coolingthe molten glass obtained by melting the block 12 of glass raw material,the positional change of the molten glass can be restricted. Thus, thecontact of the molten glass with the forming die 10 can be restrained.As a result, the precipitation of crystals in a produced glass materialcan be restrained.

From the viewpoint of more effectively reducing the positional change ofthe molten glass, the control gas is preferably jetted so that themolten glass rotates and more preferably jetted so that the molten glassrotates on a central axis passing through the molten glass (for example,a central vertical axis thereof).

Hereinafter, a description will be given of other exemplary preferredembodiments of the present invention. In the descriptions below,elements having functions substantially in common with the firstembodiment will be referred to by the common reference signs and furtherexplanation thereof will be omitted.

Second Embodiment

FIG. 4 is a schematic plan view showing a portion of the glass materialmanufacturing device according to a second embodiment.

As shown in FIG. 3, a description in the first embodiment has been givenof an example where a single control gas jet hole 10 c is provided.However, the present invention is not limited to this configuration.

As shown in FIG. 4, the second embodiment is different from the firstembodiment in that a plurality of control gas jet holes 10 c areprovided. Specifically, the plurality of control gas jet holes 10 c areprovided radially from the center of the forming surface 10 a in planview. The plurality of control gas jet holes 10 c are provided atapproximately regular intervals along the circumferential direction. Byproviding the plurality of control gas jet holes 10 c in this manner,the positional change of the molten glass can be more effectivelyrestricted. Accordingly, the contact of the molten glass with theforming die 10 can be more effectively restrained.

Furthermore, by providing the plurality of control gas jet holes 10 calong the circumferential direction, the rotation, vibration oroscillation of the block 12 of glass raw material can be promoted. Thus,the surface of the block 12 of glass raw material can be more uniformlyirradiated with laser light.

From the viewpoint of further promoting the rotation of the block 12 ofglass raw material, as shown in FIG. 5, the control gas jet holes 10 care preferably provided to extend along a direction different from theradial direction of the forming surface 10 a of the forming die 10.

Third Embodiment

FIG. 6 is a schematic cross-sectional view of a glass materialmanufacturing device according to a third embodiment.

In the first and second embodiments, a description has been given of anexample where control gas is jetted along the horizontal direction.However, the present invention is not limited to this.

As shown in FIG. 6, the third embodiment is different from the first andsecond embodiments in that a control gas jet nozzle 10 d having acontrol gas jet hole 10 c extends diagonally downward to the center ofthe forming surface 10 a of the forming die 10. Thus, control gas isjetted to the block 12 of glass raw material from an upper diagonalposition. In this case, the block 12 of glass raw material can berotated, for example, on a central horizontal axis thereof.

If the block 12 of glass raw material is not rotated, the top surface ofthe block 12 of glass raw material is heated but the bottom surfacethereof is cooled by the levitation gas jetted through the levitationgas jet holes 10 b, which makes the block 12 of glass raw materiallikely to cause temperature unevenness. Therefore, undesirablevolatilization or the generation of unmelted matter may occur. Unlikethis, since in the third embodiment the block 12 of glass raw materialis rotated on a central horizontal axis thereof, the occurrence oftemperature unevenness in the block 12 of glass raw material can bereduced.

Fourth Embodiment

FIG. 7 is a schematic cross-sectional view of a glass materialmanufacturing device according to a fourth embodiment. FIG. 8 is aschematic plan view showing a portion of the glass materialmanufacturing device according to the fourth embodiment.

In the fourth embodiment, a plurality of control gas jet nozzles 10 dhaving their respective control gas jet holes 10 c are arranged atapproximately regular intervals along the circumferential direction.Each control gas jet nozzle 10 d extends along the vertical direction.Therefore, control gas is jetted along an opposite (downward) directionto the (upward) direction of jetting of the levitation gas. Because theplurality of control gas jet nozzles 10 d are arranged so that controlgas jetted from their respective control gas jet nozzles 10 d hits theside surface of the block 12 of glass raw material, the positionalchange of the molten glass obtained by melting the block 12 of glass rawmaterial can be effectively restricted.

Fifth Embodiment

FIG. 9 is a schematic cross-sectional view of a glass materialmanufacturing device according to a fifth embodiment.

In the first to fourth embodiments, a description has been given of anexample where a plurality of levitation gas jet holes 10 b open on theforming surface 10 a. However, the present invention is not limited tothis configuration. For example, like a glass material manufacturingdevice shown in FIG. 9, a single gas jet hole 10 b opening at the centerof the forming surface 10 a may be provided. Even with a singlelevitation gas jet hole 10 b, the block 12 of glass raw material or themolten glass can be held above the forming surface 10 a of the formingdie 10 by levitation gas jetted through the levitation gas jet hole 10 bconnected to a gas supply mechanism 11.

(2) Second Glass Material Manufacturing Method

First Embodiment

FIG. 10 is a schematic cross-sectional view of a glass materialmanufacturing device 1 a according to a first embodiment. As shown inFIG. 10, the glass material manufacturing device 1 a includes a formingdie 10. The forming die 10 has a curved forming surface 10 a.Specifically, the forming surface 10 a is spherical.

The forming die 10 has gas jet holes 10 b opening on the forming surface10 a. Specifically, in this embodiment, a plurality of gas jet holes 10b are provided. More specifically, like the first embodiment (FIG. 2) ofthe first glass material manufacturing method, the plurality of gas jetholes 10 b are arranged radially from the center of the forming surface10 a.

The forming die 10 may be made of a porous body having interconnectedcells. In this case, the gas jet hole 10 b is formed of interconnectedcells.

The gas jet holes 10 b are connected to a gas supply mechanism 11, suchas a compressed gas cylinder. Gas is supplied from this gas supplymechanism 11 via the gas jet holes 10 b to the forming surface 10 a. Agas flow regulating portion 11 a is provided between the gas supplymechanism 11 and the gas jet holes 10 b. By this gas flow regulatingportion 11 a, the flow rate of gas to be jetted out through the gas jetholes 10 b can be controlled. The gas flow regulating portion 11 a canbe formed of, for example, a valve.

As the gas, the same type as that used in the first embodiment of thefirst glass material manufacturing method can be used.

In manufacturing a glass material using the manufacturing device 1 a,first, a block 12 of glass raw material is placed on the forming surface10 a. The form and shape of the block 12 of glass raw material are thesame as in the first embodiment of the first glass materialmanufacturing method.

Next, gas is jetted out through the gas jet holes 10 b, thus levitatingthe block 12 of glass raw material above the forming surface 10 a. Inother words, the block 12 of glass raw material is held, out of contactwith the forming surface 10 a, in the air. In this state, the block 12of glass raw material is irradiated with laser light from a laserapplicator 13. Thus, the block 12 of glass raw material is heated andmelted to make it vitrifiable, thereby obtaining a molten glass.Thereafter, the molten glass is cooled, so that a glass material can beobtained. During the step of heating and melting the block 12 of glassraw material and the step of cooling the molten glass and in turn theglass material at least to below the softening point, at least thejetting of gas is preferably continued to restrain the contact of theblock 12 of glass raw material, the molten glass or the glass materialwith the forming surface 10 a. Note that in the description below thestep of irradiating the block 12 of glass raw material or a melt of theblock 12 of glass raw material with laser light is referred to as a“melting step”. Therefore, the melting step can include: the process ofirradiating the block 12 of glass raw material with laser light to meltthe block 12 of glass raw material; and the process of irradiating amolten glass obtained by melting the block 12 of glass raw material withlaser light to homogenize the molten glass.

The inventors have found, as a result of intensive studies, that if theflow rate of gas during the melting step is constant, the levitatedstate of the block 12 of glass raw material or the molten glass changes.Specifically, for example, if the flow rate of gas is set such that theblock 12 of glass raw material is stably levitated, the flow rate of gasis too large, which may cause the molten glass to be excessivelyvibrated or oscillated and thereby be likely to come into contact withthe forming die 10. On the other hand, if the flow rate of gas is setsuch that the molten glass is stably levitated, the flow rate of gas istoo small, which may make the block 12 of glass raw material difficultto levitate sufficiently. If the levitation of the block 12 of glass rawmaterial is insufficient, a melted portion of the block 12 of glass rawmaterial may come into contact with the forming die 10 and therebybecome a starting point of crystallization. Furthermore, because theblock 12 of glass raw material is less likely to change in position, aparticular portion thereof is likely to be locally heated, which maycause a composition deviation due to evaporation of a glass component.

In this embodiment, the gas flow regulating portion 11 a makes the flowrate of gas through the gas jet holes 10 b after the melting of theblock 12 of glass raw material smaller than the flow rate of gas throughthe gas jet holes 10 b before the melting of the block 12 of glass rawmaterial. Therefore, both the block 12 of glass raw material and themolten glass obtained by melting the block 12 of glass raw material canbe suitably levitated. Thus, the block 12 of glass raw material and themolten glass can be restrained from coming into contact with the formingdie 10.

Specifically, in this embodiment, as shown in FIG. 11, the flow rate ofgas jetted to the block 12 of glass raw material before the start of themelting step is set at L1. The flow rate of gas jetted to the moltenglass after the block 12 of glass raw material has been completelymelted is set at L2 smaller than L1. Thereafter, the jetting of gasthrough the gas jet holes 10 b is stopped. By doing so, the generationof crystals and nuclei in the molten glass can be restrained. Therefore,a homogeneous glass material can be produced.

The flow rate of gas is preferably reduced from L1 to L2 before theblock 12 of glass raw material has been completely melted, and the flowrate of gas is preferably reduced from L1 to L2 in a period from thetime when the melting of the block 12 of glass raw material starts tothe time when the block 12 of glass raw material has been completelymelted into a molten glass. By doing so, the molten glass can be moreeffectively restrained from coming into contact with the forming die 10.

From the viewpoint of obtaining a more homogeneous glass material, L1/L2is preferably 1.05 to 1.5 and more preferably 1.1 to 1.2. The flow ratesL1 and L2 can be appropriately set depending on, for example, the shapeor dimension of the block 12 of glass raw material or the shape or otherfeatures of the gas jet holes 10 b and can be set at, for example, about0.5 L/min to about 15 L/min.

Second Embodiment

FIG. 12 is a schematic cross-sectional view of a glass materialmanufacturing device 1 a according to a second embodiment.

In the first embodiment, a description has been given of an examplewhere a plurality of gas jet holes 10 b open on the forming surface 10a. However, the present invention is not limited to this configuration.For example, like a glass material manufacturing device 1 b shown inFIG. 12, a single gas jet hole 10 b opening at the center of the formingsurface 10 a may be provided.

Third Embodiment

FIG. 13 is a time chart of the flow rate of gas in a third embodiment.As shown in FIG. 13, in this embodiment, the flow rate of gas throughthe gas jet holes 10 b is increased in the cooling step after theirradiation of laser light is stopped. Specifically, in the cooling stepafter the irradiation of laser light is stopped, the flow rate of gas isincreased from a flow rate L2 in the melting step to a flow rate L3larger than L2. By doing so, the formed glass material can be keptstably levitated in the cooling step. For example, if the flow rate ofgas remains at the flow rate L2 even in the cooling step, the formedglass material may not stably be levitated. This can be attributed tothe fact that the glass material formed by cooling is difficult tolevitate because it has a higher density and has a smaller surface areaand therefore a smaller area exposed to gas than the mass of glass in amelted state. The ratio of the flow rate L3 to the flow rate L2 ispreferably 1.05 to 1.5 and more preferably 1.1 to 1.2. Specifically, theflow rate L3 varies depending on the shape, dimension or other featuresof the block 12 of glass raw material, but is preferably, for example,about 1 L/min to about 15 L/min.

The flow rate L3 is more preferably less than the flow rate L1. Thereason for this is that while generally the block 12 of glass rawmaterial is porous or has a distorted shape, the formed glass materialis solid and has a neat shape, thereby requiring a less flow rate of gasfor levitation. Specifically, the ratio of the flow rate L3 to the flowrate L1 is preferably 0.98 or less and more preferably 0.95 or less.

(3) Third Glass Material Manufacturing Method

First Embodiment

In this embodiment, like the first embodiment of the second glassmaterial manufacturing method, a glass material is manufactured usingthe manufacturing device 1 a shown in FIG. 10.

As the gas, the same type as that used in the first embodiment of thefirst glass material manufacturing method can be used.

Next, a description will be given of a glass material manufacturingmethod using the manufacturing device 1 a. What is performed in thisembodiment are: a melting step of placing a block 12 of glass rawmaterial on the forming surface 10 a of the forming die 10, melting theblock 12 of glass raw material by irradiating the block 12 of glass rawmaterial with laser light from the applicator 13 while jetting gasthrough the gas jet holes 10 a opening on the forming surface 10 a, thusobtaining a molten glass, and then homogenizing the molten glass; and acooling step of cooling the molten glass to obtain a glass material. Inthe melting step, the irradiation with the laser light is started withthe block 12 of glass raw material in contact with the forming surface10 a and the block 12 of glass raw material is then levitated above theforming surface 10 a by the gas.

The form and shape of the block 12 of glass raw material are the same asin the first embodiment of the first glass material manufacturingmethod.

FIG. 14 is a time chart of the flow rate of gas and the intensity oflaser light in the first embodiment. In this embodiment, as shown inFIG. 14, the gas starts being jetted concurrently with the start ofirradiation with laser light. In this case, just after the block 12 ofglass raw material starts being irradiated with laser light, the flowrate of gas is controlled so that the block 12 of glass raw material isin contact with the forming surface 10 a. Specifically, after the gasstart being jetted concurrently with the start of irradiation with laserlight, the flow rate of gas is gradually increased and then, uponcompletion of the melting of the block 12 of glass raw material andturning thereof into a molten glass, controlled to reach a flow rate L1suitable to stably levitate the molten glass. Thereafter, this state ismaintained for a given time for glass homogenization. Then, theirradiation with laser light is stopped and the molten glass is cooled,so that a glass material can be obtained.

It is preferred that until the molten glass and in turn the glassmaterial reaches at least below the softening point after the completionof melting of the block 12 of glass raw material, at least the jettingof gas should be continued to restrain the contact of the molten glassor the glass material with the forming surface 10 a. Furthermore, instopping the jetting of gas, the flow rate of gas is preferablygradually reduced.

The flow rate L1 can be appropriately set depending on, for example, theweight or volume of the block 12 of glass raw material or the shape,dimension or other features of the gas jet holes 10 b. The flow rate L1can be set at, for example, about 0.5 L/min to about 15 L/min.

Note that in this embodiment the step of irradiating the block 12 ofglass raw material or the molten glass obtained by melting the block 12of glass raw material with laser light is referred to as a “meltingstep”. Therefore, the melting step can include: the process ofirradiating the block 12 of glass raw material with laser light to meltthe block 12 of glass raw material; and the process of irradiating amolten glass obtained by melting the block 12 of glass raw material withlaser light to homogenize the molten glass.

As thus far described, in this embodiment, just after the block 12 ofglass raw material starts being irradiated with laser light, the block12 of glass raw material is in contact with the forming surface 10 a.Particularly, in this embodiment, during a period from just after thestart of irradiation of the block 12 of glass raw material with laserlight to the completion of melting of the block 12 of glass rawmaterial, the block 12 of glass raw material is in contact with theforming surface 10 a and, therefore, less likely to vary in position.For this reason, the state of irradiation of the block 12 of glass rawmaterial with laser light can be substantially similar among lots.Hence, a glass material small in variations in properties among lots canbe manufactured.

In this embodiment, the gas starts being jetted concurrently with thestart of irradiation with laser light. By doing so, the rise in thetemperature of the forming die 10 can be reduced by the cooling effectof the gas. As a result, the molten glass can be restrained from fusionbonding to the forming surface 10 a of the forming die 10.

In this embodiment, the flow rate of the gas is gradually increased to aflow rate L1 at which the block 12 of glass raw material becomeslevitated. Therefore, the abrupt change in the flow rate of the gasjetting to the block of glass raw material can be reduced, so thatsudden movements of the block 12 of glass raw material (or the moltenglass) can be effectively restrained.

In this embodiment, after the melting of the block 12 of glass rawmaterial is completed, gas is jetted so that the molten glass islevitated. Therefore, the molten glass can be restrained from cominginto contact with the forming surface 10 a and thus being crystallized.Hence, a glass material having more excellent homogeneity can bemanufactured.

Second Embodiment

FIG. 15 is a time chart of the flow rate of gas and the intensity oflaser light in a second embodiment.

In the first embodiment, a description has been given of an examplewhere the flow rate of gas reaches L1 when the melting of the block 12of glass raw material is completed. However, the present invention isnot limited to this. For example, as shown in FIG. 15, after the meltingof the block 12 of glass raw material starts and before the block 12 ofglass raw material is completely melted, the gas may be jetted so thatthe flow rate of the gas reaches L1. In this case, a melted portion ofthe block 12 of glass raw material can be restrained from coming intocontact with the forming surface 10 a and thus precipitating crystals.

Third Embodiment

FIG. 16 is a time chart of the flow rate of gas and the intensity oflaser light in a third embodiment.

In the first and second embodiments, a description has been given of anexample where the flow rate of gas is gradually increased until theblock 12 of glass raw material starts being levitated. However, thepresent invention is not limited to this. For example, as shown in FIG.16, the flow rate of gas may be stepwise increased until the block 12 ofglass raw material starts being levitated. Also in this case, the abruptchange in the flow rate of gas jetting to the block 12 of glass rawmaterial can be reduced.

Furthermore, in the first and second embodiments, a description has beengiven of an example where the gas starts being jetted concurrently withthe start of irradiation with laser light. However, the presentinvention is not limited to this. For example, as shown in FIG. 16, thegas may start being jetted after the start of irradiation with the laserlight. In this case, variations in the position of the block 12 of glassraw material can be more effectively reduced.

Fourth and Fifth Embodiments

FIG. 17 is a time chart of the flow rate of gas and the intensity oflaser light in a fourth embodiment. FIG. 18 is a time chart of the flowrate of gas and the intensity of laser light in a fifth embodiment.

In the first and second embodiments, a description has been given of anexample where gas starts being jetted concurrently with the start ofirradiation with laser light. Furthermore, in the third embodiment, adescription has been given of an example where the gas starts beingjetted after the start of irradiation with laser light. However, thepresent invention is not limited to these. For example, as shown inFIGS. 17 and 18, before the block 12 of glass raw material starts beingirradiated with laser light, the gas may be jetted at such a flow ratethat the block 12 of glass raw material can be held in contact with theforming surface 10 a. In this case, the rise in the temperature of theforming die 10 can be more effectively reduced.

Sixth Embodiment

FIG. 19 is a time chart of the flow rate of gas and the intensity oflaser light in a sixth embodiment.

In the first to fifth embodiments, a description has been given of anexample where the intensity of laser light is gradually increased sothat the melting of the block 12 of glass raw material is completed atthe time when the intensity of laser light reaches the maximum. However,the present invention is not limited to this. For example, as shown inFIG. 19, the intensity of laser light may be gradually increased to amaximum intensity so that the melting of the block 12 of glass rawmaterial is completed after the intensity of laser light reaches themaximum.

Seventh Embodiment

FIG. 20 is a time chart of the flow rate of gas and the intensity oflaser light in a seventh embodiment.

In the first to sixth embodiments, a description has been given of anexample where the intensity of laser light is gradually increased to amaximum intensity. However, the present invention is not limited tothis. For example, as shown in FIG. 20, the intensity of laser light maybe stepwise increased from zero to the maximum intensity.

Eighth Embodiment

In the first to seventh embodiments, a description has been given of anexample where a plurality of gas jet holes 10 b open on the formingsurface 10 a of the forming die 10. However, the present invention isnot limited to this configuration. For example, like the glass materialmanufacturing device 1 b shown in FIG. 12, a single gas jet hole 10 bopening at the center of the forming surface 10 a may be provided.

REFERENCE SIGNS LIST

-   1, 1 a, 1 b manufacturing device-   10 forming die-   10 a forming surface-   10 b levitation gas jet hole-   10 c control gas jet hole-   10 d control gas jet nozzle-   11 gas supply mechanism-   11 a gas flow regulating portion-   12 block of glass raw material-   13 laser applicator

1. A glass material manufacturing method comprising: a melting step ofplacing a block of glass raw material on a forming surface of a formingdie, melting the block of glass raw material by irradiating the block ofglass raw material with laser light while jetting gas through a gas jethole opening on the forming surface, thus obtaining a molten glass, andthen homogenizing the molten glass; and a cooling step of cooling themolten glass, wherein the irradiation with the laser light is startedwith the block of glass raw material in contact with the forming surfaceand the block of glass raw material is then levitated above the formingsurface by the gas.
 2. The glass material manufacturing method accordingto claim 1, wherein the gas is jetted so that the block of glass rawmaterial starts being levitated when or before the melting of the blockof glass raw material is completed.
 3. The glass material manufacturingmethod according to claim 1, wherein a flow rate of the gas is graduallyincreased until the block of glass raw material starts being levitated.4. The glass material manufacturing method according to claim 1, whereina flow rate of the gas is stepwise increased until the block of glassraw material starts being levitated.
 5. The glass material manufacturingmethod according to claim 1, wherein the gas starts being jettedconcurrently with the start of irradiation with the laser light.
 6. Theglass material manufacturing method according to claim 1, wherein thegas starts being jetted after the start of irradiation with the laserlight.